I try to figure out the best way to seal the mesh in my 4 person dome tent.

Looking at some posts possible solution is clamping a blanket or a sheet over the mesh areas of the tent.- what would be better, a fleece blanket or just an old sheet? Do simple sheets block the dust?- is it a must to get the cover blanket/sheet tight close to the tent material? (... a bit difficult since the external poles do not allow the cover to be tight on the tent).

Similarly if I choose to stitch material over the mesh - will old sheets be sufficient?

I used pieces of wool blanket cut to fit the mesh sections. If you have time wrap stitch the edges of the blanket to the outline of the mesh with fairly heavy thread...it's a little tighter than clamps. Does a great job minimizing dust sifting in from overhead.

Don't bore your friends with all your troubles. Tell your enemies instead, for they will delight in hearing about them.

When I was using tents I used muslin, either hot glued, safety pinned or velcroed to the tent. The pest tip I can give you is put the sheeting on the outside of the tent not on the inside, and always leave a some mesh uncovered to give your self some ventilation (like the door). I tried old sheets and various plastics. The plastics did well keeping dust out, but made the tent feel like being inside a rubber glove. The old sheets did well, but I liked the muslin best. A bit of dust did come through, but it breathed while keeping out 90% of the dust without the muslin, so I think it was a good trade off.

My advice: forget about it, dust will enter your tent anyway. Don't waste any time taping and sealing, just get a big plastic tub with a lid and put all your things in there. Roll up your sleeping bag when you're not using it.

Been there, done that. Taping mylar to the outside of your tent is a good way of making lametta in just a short wind storm.

Besides, what are you doing in your tent anyway? The playa is out there!